How much of a differance in gas milage will there be between a 245/75 17 and a 285/70/17. My mpg is already not very good ( 11 or 12 all the time unless the whole tank is on the highway) Will the 285 make it drop even more?

 

You either have a really heavy foot or something wrong. What (if any) mods are you running? Realistically with stock tires and no mods, you should be able to pull down at least 14, even with a heavy foot.

The different between 245 and 285... maybe a couple of tens less.

 

I get around 13 in town and have got 16-17 on highway on a full tank.I have 285's,5.4 a k@n and a programmer.I dont think the programmer or the K@n make much difference in that milage.I was thinking 13 or so in town was average for the 5.4

 

I'm running a SuperChips programmer and I would disagree that the programmer doesn't have an effect, my mileage went up a full mpg on the baseline setting, 2 when set for towing - of course that setting requires 91 octane or better, but the mileage improvement more than pays for the more expensive gas.

 

I just gassed up yesterday and averaged 16.1 mpg. I have a drop in K& N filter.
Douglas

 

I've always heard that the programmers made a difference in gas,I just never saw any change.Mine is acually a troyer custom tune.

 

I was getting 17.4 with 275/65/18 tires then I got the new 305/65/18 and I have lost 2 miles and counting down to 15.2 right now.

 

I have been pretty good about not stomping on it but my milage is still not great. the best I have ever gotten is 17mpg on a 400 mile highway trip. I have a 5.4 scabwitha drop in K & N ( i didnt notice any improvement) around town the best i ever averaged back and forth from work was 13mpg. I want the 285 tires but I dont want the mpg to go in the toilet.

 

Just a K & N drop in otherwise it is all stock. 5.4 Scab and a fold a cover bed cover.

 

i get 11 and 12 also, brand new 06 screw, im questioning the same thing

 

The other part of heavy foot is speed - I see a noticable difference with mpg from 60 to 70 to 80 (disclaimer - closed course not on public roadways). You probably won't notice much difference at all with that difference. I see about 1 mpg less with 325/60/18 versus the stock 265. That is with the programmer correcting for diameter.